1. Field of the Invention
This invention generally relates to the field of transmission assemblies for four-wheel recreational vehicles. More particularly, the present invention relates to a gear shift assembly for shifting the gears of an all-terrain vehicle (ATV) transmission.
2. Description of Related Art
FIGS. 1A and 1B illustrate a straddle-type vehicle 1, such as an all terrain vehicle or ATV, including front wheels 6 and rear wheels 8 suspended on a front end and on a rear end, respectively, of a body frame 4. Handlebars 5 and a seat 11 are mounted on the frame 4. A power unit such as an engine 20 is also mounted on the frame 4 and generates the power required to propel the ATV 1. A transmission 22 is provided to transfer the power generated by the engine 20 to the front wheels 6, the rear wheels 8 or both the front and rear wheels 6, 8 to drive the ATV 1.
Generally, the transmission of an ATV includes a number of different components to efficiently transmit engine power to front and/or rear wheels of the vehicle. In particular, transmission gears are provided for accelerating and decelerating the ATV and include lower gears and higher gears. A clutch is also provided for engaging/disengaging the gears in order to facilitate shifting. The clutch includes a number of different clutch plates that must be opened (separated) for the clutch to properly engage/disengage the gears. Finally, a shifter is provided for permitting an ATV operator to operate the clutch, and thereafter change the gears. One popular type of shifter used in conventional ATV transmissions is a mechanical foot lever assembly, an example of which is illustrated in FIG. 2.
As shown in FIG. 2, a foot shifter 72 is adapted to be operatively connected or linked to the clutch and a gear box (not shown), respectively. Upon actuation of the foot lever, for example, up-shifting or down-shifting, the clutch can be initiated and actuated, i.e., the clutch plates are moved out of engagement with one another. Upon further actuation of the foot lever, the gear box can be initiated and actuated, i.e., a plurality of gears is shifted.
The footshifter must be rotated distance D1 in order to initiate and actuate the clutch, as described above. After the footshifter is rotated distance D1, the operator must rotate the footshifter a further distance D2 to initiate and actuate the gear box while actuating the clutch. The foot shifter 72 must be displaced over a distance D1+D2 in order to carry out a gear changing operation. As illustrated, the distance D1+D2 is a rotational or angular distance, but for the sake of simplicity, the distance D1+D2 could be shown schematically as a linear distance for example.
The amount of work (W) required by the ATV operator to complete the gear shifting of a conventional ATV, having a foot lever assembly as illustrated in FIG. 2, is defined by the following formula: (W)=(F)*(d), where (d) is a displacement distance, typically expressed in meters, which the foot lever must travel in order to operate the clutch and to change gear of the transmission and (F) is an amount of force, typically expressed in Newtons, which is required to move the foot lever through distance (d), which is typically expressed in meters. Thus, in some circumstances, a considerable amount of work (W), which is measured in joules (J), may be required for the ATV operator to use the foot lever 72 to change the gears. This is especially true when the foot lever 72 must travel a large distance to shift the gears. It is also true when a large amount of force (F) must be applied to the foot lever to complete the shift. Tables 1 and 2 illustrate these principles in conventional ATVs.
Table 1 illustrates foot lever displacement distances (d), the amount of required force (F), and the total amount of work (W) required to complete a gear shift in conventional ATVs from four different manufacturers. Gear shift motions include two types. Typically, shifting from a lower gear to a higher gear is called an up-shift and shifting from a higher gear to a lower gear is called a down-shift. Table 1 illustrates up-shifting results and Table 2 illustrates down-shifting results.
FIG. 3 illustrates a computer controlled shifting mechanism, generally indicated at 71, in related art that requires little effort from the ATV operator to shift gears. The shifting mechanism is mounted onto a handlebar of a conventional ATV. The problem, however, with computer controlled shifters, especially handlebar-mounted configurations, is that they sometimes do not provide the operation with a feeling of complete control over the shifting operation, which some operators believe results in an unnatural feel. That is, most ATV operators consider the mechanical foot lever more enjoyable and sportier than the purely electronic shifters.
A need has developed for a gear shift assembly that combines the benefits of a mechanical foot shifter with a modicum of computer control so that a vehicle operator, such as an ATV operator, need not exert a large amount of work to shift the vehicle""s gears.
Consistent with the principles of the present invention as embodied and broadly described herein, one embodiment includes a vehicle comprising an engine, a gear box operatively coupled to the engine and a clutch assembly operatively coupled to the gear box. A foot shifter assembly is operatively coupled to at least one of the clutch assembly and the gear box and is displaceable over a predetermined distance (d). The predetermined distance (d) permits the shifting of the gears using a predetermined amount of work (W), the predetermined amount of work being defined by the following expression: W=(F)*(d). W is one of a group consisting of less than about 5.3 joules for an up-shift and less than about 5.0 joules for a down-shift.
In another embodiment, a vehicle comprises a plurality of wheels, an engine operatively coupled to at least one of the plurality of wheels to impart a driving rotation thereto and a clutch assembly operatively connected to the engine. A gear box is configured to shift gears and being operatively connected to the clutch assembly. A foot shifter assembly is operatively connected to the clutch assembly and the gear box and is displaceable over a predetermined distance to actuate both the clutch and the gear box. Displacement of the foot shifter assembly through the predetermined distance actuates the clutch and the gear box to shift gears.
Yet another embodiment includes a gear shift assembly for a straddle-type vehicle including a power unit having a transmission assembly having a plurality of gears for transmitting power to at least one wheel. The gear shift assembly comprises a foot shifter assembly operatively connected to the transmission assembly and selectively displaceable over a predetermined distance, for example, by a vehicle operator. A shift rod has a first end attached to the foot shifter assembly and a second end configured to transfer motion when the foot shifter assembly is displaced over the predetermined distance. A shift lever is linked to the second end of the shift rod and has a notch formed therein. A clutch has a plurality of clutch plates configured to engage and disengage the gears. An electrical switch is associated with the clutch and configured to open the clutch plates. The electrical switch has a trigger operatively associated with the notch. Movement of the shift lever actuates the electrical switch to open and close the clutch plates.
Another embodiment includes an apparatus comprising a straddle-type vehicle including a body frame supported by front and rear wheels. A seat is supported above the frame and a power unit is supported by the frame below the seat. The power unit has a transmission including gears. A foot shifter is operatively attached to the power unit and is selectively displaced over a predetermined distance (d) upon application of a predetermined amount of force (F) by a vehicle operator. The selective movement of the foot shifter assembly thereby shifts the gears. The selective displacement includes an up-shift and a down-shift. The predetermined distance (d) permits the shifting of the gears using a predetermined amount of work (W) and the predetermined amount of work is defined by the following expression: W=(F)*(d). W is one of a group consisting of less than about 5.3 joules for an up-shift and less than about 5.0 joules for a down-shift.
In one preferred embodiment, W is less than about 5.3 joules for an up-shift and less than about 5.0 joules for a down-shift.
Other objects of the present invention will be revealed by the discussion that follows.